This invention is concerned with the handling of crop material normally discharged onto the ground during harvesting operation with a combine harvester and, in particular, an arrangement for spreading more widely and uniformly the chaff discharge from the cleaning shoe of the combine.
In typical combine harvester operation, with machines of generally conventional configuration, there are two main discharges from rearward portions of the machine. The cleaning shoe discharge consists principally of chaff, usually from an upper chaffer screen, and is normally allowed to fall in a band approximately equal to the width of the body of the combine. From the separating mechanism, whether straw walkers or the axial flow rotary type, the discharge of straw normally passes above and rearwardly of the chaff discharge. In many cases, the straw is directed into a distributing device which may be a simple spreader or a chopper which chops the straw into shorter lengths as well as spreading it over a width greater than that of the body of the combine.
Because of changing cultural practices and environmental concerns, there is a growing interest in and need for means for spreading the chaff as well as the straw uniformly over the field during harvesting operation. When harvesting with a cutting platform, spreading width should be equal to the width of cut of the platform. The presence of large quantities of crop residue, unevenly spread on the field surface, is generally incompatible with the so-called minimum tillage cropping practices now becoming increasingly popular. Removal by burning was a solution but is now widely prohibited because of environmental concerns. Further, it has so far not often been cost effective to collect and remove grain harvest residues from the field for a "by-product" use such as biomass conversion or in livestock management. Consequently, most growers have little choice but to incorporate most of their harvest residues into the soil. The effects of incorporation are varied and not always beneficial. In the long run, in lighter soils particularly, the soil may be improved by an increase in organic matter content but, on heavier soils, yields may be depressed and there may be an increase of pest and disease problems. But it is widely accepted that to minimize problems and optimize possible beneficial effects, chopping of the straw and uniform distribution of all of the residue is essential.
Chaff is a light and fluffy material and difficult to spread, in a controlled fashion, laterally beyond the conventional swath deposited behind the combine. Druffel, U.S. Pat. No. 4,137,923 attempts simple lateral projection of the chaff independently of the straw by placing a pair of laterally directed fans, one on each side of the chaff discharge from the combine cleaning shoe. Straw, (especially when chopped) is relatively "heavier", making controlled spreading more feasible and manageable and both Tessman (U.S. Pat. No. 3,450,286) and Linn (U.S. Pat. No. 4,292,795) recognize the possibilities of carrying chaff further by mixing it with straw in the straw chopper. Tessman discusses this principally as an improved way of collecting residues, by blowing them into a wagon trailing behind the combine, but Linn recognizes the usefulness of the method for improving spreading. He suggests that the mixing of the chaff with the straw being chopped and distributed by the blades of the straw chopper causes it to be "distributed a much further distance on either side of the machine and relatively evenly over the ground thus preventing undesirable concentrations of chaff component". Both Tessman and Linn rely on endless belt-type conveyors to convey chaff from the cleaning shoe to the straw chopper and these have the disadvantage of relatively high cost and weight as well as being difficult to install without hindering access to the cleaning shoe for adjustment and to other parts of the combine for service or repair. Also, their bulk may adversely affect air flow patterns at the shoe, especially in the discharge area.
Gaeddert (U.S. Pat. No. 3,669,123) is also more concerned with "utilizing the heretofore wasted nutritional qualities of stover (chaff)" and mixing it with the straw chopper output for collection as livestock fodder rather than distribution to facilitate future cropping operations. However, Gaeddert does disclose an arrangement whereby the chaff is essentially induced into the discharge of a transverse-rotor straw chopper. However, he discloses only combine configurations in which proximity of the rear end of the cleaning shoe to the straw chopper makes possible a form of gravity transfer using only a simple agitated slide.
In what may be considered a variation on Gaeddert, Anderson, in Farm Show, Vol. 8, No. 3, 1984, page 6, discloses a shoe extension for carrying chaff to the impellers of a straw spreader for mixing the chaff with the straw for better spreading. However, this method must interfere with access to the cleaning shoe and does not appear to be readily adaptable to a variety of combine sizes and types or to being used to feed a straw chopper rather than a spreader.
A common disadvantage of the arrangements described above is that they all are designed to transfer, without discrimination, the total discharge from the cleaning shoe chaffer screen. This flow of material may, of course, include matter which is better excluded from the straw distributor or chopper, such as foreign bodies of metal or stone which may cause damage and are certainly better excluded if the material is being collected for livestock feeding.